In this video, Mr. Khan draws a box and two intersecting lines that produce several triangles. Mr. Khan proves that the area of these diagonal-generated triangles of the rectangle are equal. He goes over the formula for finding the area of a triangle.... Sal Khan is the recipient of the 2009 Microsoft Tech Award in Education. The screen gets busy (and dark)--the viewer may want to open to 'full screen' to see everything. The sound is a little low. (04:35)[more]

Multiple proofs showing that a point is on a perpendicular bisector of a segment if and only if it is equidistant from the endpoints. Then, using this to establish the circumcenter, circumradius, and circumcircle for a triangle. (12:29)

This slide show presentation explores the properties of triangles, classifying them, and models solving several problems involving triangles. This is part of a textbook series put out by Glenco/ McGraw-Hill.

Video uses an electronic black board with different colored pens. This video is an introduction to similar triangles. The person discusses the meaning of the term similar then goes on to discuss similar triangles (they have all the same angles), and... why they are considered similar (ratio of corresponding sides is the same). Video then gives examples to help students understand the terms used and how to find similar angles. Good quality video. Good for middle elementary and middle school students. (09:34)[more]

This learning shapes video from Little Runners focuses on the attributes of triangles. It shows a picture on the screen of a triangle and a voice talks about the corners and sides of triangles. The video ends with animated images of real-life example...s of triangles. Very clear teaching. (02:04)[more]

In this vdeo students learn the following theorems related to parallel lines. If 3 parallel lines form congruent segments along one transversal, then they form congruent segments along every transversal. If a line intersects the midpoint of one side ...a triangle and is parallel to another side of the triangle, then it intersects the midpoint of the third side of the triangle. If a segment joins the midpoints of two sides of a triangle, then the segment is (a) parallel to the third side of the triangle, and (b) half the length of the third side. Students are then asked to solve problems related to these theorems using Algebra.[more]

The instructor uses a smartboard to demonstrate what overlapping triangles are and their properties. The room is dark, hence the video is a little dark. The instructor teaches grade 9 Geometry at Martin Luther High School in Maspeth, NY. (01:13)

Identify the properties of two- and three- dimensional geometric figures using appropriate terminology and vocabulary. Classify triangles ad scalene, isosceles, or equilateral.

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